Download - Approach to Renal Stones - AMS
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Approach to Renal Stones College of Medicine Physician Course 2013
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Outline
• Epidemiology • Presentation and Pathogenesis • Contributing factors • Evaluation • Management strategies • Summary
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Epidemiology • USA (NHANES data 2007-2010)
Scales et al. European Urology 2012
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Incidence and Prevalence • Annual incidence 0.6-1.5%
• Prevalence 2-7%
• Lifetime risk 10-20%
• Male>Female
• Caucasians>Hispanics and Asians>African Americans
• No data available for Asia
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Clinical presentation • Asymptomatic • Abdominal pain • Haematuria • Urinary tract infection • CKD/ESRD
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Stone types
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Pathogenesis
• Supersaturation • Imbalance of modifiers • Epithelial factors
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Supersaturation
• Ratio urinary Calcium Oxalate or Calcium Phosphate concentration: solubility
• At levels <1 crystals dissolve • At levels >1 crystals can nucleate and grow
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Imbalance of modifiers • Anatomical factors
o Urinary stasis - caused by ureteropelvic junction obstruction, horseshoe kidney or polycystic kidneys
• Hypercalciuria o Usually familial or idiopathic o Would a low Ca diet help?
• Calcium binds oxalate in the gut hindering its absorption therefore low Ca diet may actually result in increased Ca Oxalate stone formation!
• Hypocitraturia - increases risk of stone formation o can occur in distal RTA, hypokalaemia, carbonic anhydrase
inhibitor use (topiratmate) • Hyperuricosuria
o due to increased purine intake o promotes calcium stones by decreasing Ca Oxalate solubility
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Epithelial factors
• Stones can form over regions of interstitial CaPhosphate deposits on the papillary surface (Randall’s plaques); usually in idiopathic CaOxalate recurrent stone formers
• Idiopathic CaPhosphate stones tend to form over the inner medullary collecting ducts that contain apatite or other crystals
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Contributing factors • Obesity • Lower
socioeconomomic status
• Metabolic syndrome
Scales et al. European Urology 2012
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Associated Factors (Ca stones)
Worcester, Coe. NEJM 2010
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Worcester, Coe. NEJM 2010
Causes of renal calculi
Calcium stones Primary Hyperparathyroidism Medullary sponge kidney Distal renal tubular acidosis Uric acid stones Acidic urine (pH<5.5) UA overproduction and secretion
Struvite stones Urease-producing organisms (proteus/klebsiella) Cystine stones Cystinuria (AR disorder)
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Evaluation • Comprehensive evaluation indicated for
o Multiple/recurrent stones
o Progressive calculi (increasing in size or number)
o Children, Non-caucasians
o Non calcium containing calculi
o Solitary kidney
o (Metabolic syndrome)
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To Evaluate or not? • Doing something
o Uncover underlying condition e.g. primary hyperparathyroidism o Associated conditions e.g. low bone density o Tailor therapy o Follow efficacy of therapy
• Doing nothing o Recurrence rate 50-60% in 10yrs; 70-80% in 20 yrs o Empirical Rx can be effective
• Increase fluid intake • Decrease salt and protein in the diet • Alkali Rx
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Imaging
Plain Xray
US
CT KUB
IVU MRI
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Two separate 24 hour urine collection, while on usual diet and activities for: Urine Vol pH Calcium Oxalate Uric acid Citrate Sodium Creatinine
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Treatment options for renal calculi
Symptoms
Conservative Surgical
Yes No
<7mm >7mm
Percutaneous nephrolithotomy Shock wave lithotripsy
Ureteroscopy Open/Laparoscopic surgery
Annual Imaging
Stones <5mm more likely to pass (p=0.006)
20% incidence of spontaneous passage
Only 7.1% required intervention eventually
Ureteric obstruction Koh LT et al. BJUI 2011
Chandrashekar K et al. AJM 2012
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Recurrence prevention
• Fluid intake
• Dietary restrictions? o Low animal protein, Na, oxalate with normal Ca intake vs low Ca and
oxalate intake 36,37
o Low sodium diet can decrease excretion of both calcium and oxalate
• Thiazides
• Potassium citrate
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Clinical trials in pharmacotherapy
Sakhaee et al.J Clin Endocrinol Metab, June 2012
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Preventative measures
Worcester, Coe. NEJM 2010
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Fluid intake
• Ensuring a urine volume of >2L/day was associated with reduced urinary supersaturation of CaOxalate and reduced stone recurrence
Borghi et al. J Urol 1996
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Dietary contributory factors
• High animal protein diet • High salt diet • High oxalate containing foods • Low calcium diet • Excessive Vit C and D • Excessive fructose intake
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Dietary interventions • Low calcium diet? • In men with recurrent
calcium oxalate stones and hypercalciuria, restricted intake of animal protein and salt, combined with a normal calcium intake, provides greater protection than the traditional low calcium diet
Borghi et al. NEJM 2002
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Thiazide diuretics
• Decreases urine calcium excretion and reduces rates of Ca stones by >50% in a 3 year period1,2,3,4
• Concurrent low salt diet (attenuates urinary calcium excretion) and sufficient potassium (to avoid hypocitraturia)5
1Borghi et al. J Cardio Phamacol 1993 2Ettinger et al. J Urol 1988 3Laerum et al. Acta Med Scand 1984 4Fernandez-Rodriguez et al. Actas Urol Esp 2006 5Pak et al. AJM1985
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Potassium Citrate • Reduces stone recurrence among patients with
hypocitraturia1,2
• Can be safely combined with a thiazide • Lowers urinary calcium excretion, raises urinary
citrate and reduces urinary CaOxalate, CaPhosphate and undissociated uric acid supersaturation3.
1Ettinger et al. J Urol 1997 2Barcelo et al. J Urol 1993
3Sakhaee et al. KI 1983
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Allopurinol
• Decreases stone recurrence in patients with idiopathic CaOxalate stones with hyperuricosuria
• Should be paired with a reduction in purine intake
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Approach to evaluation & Rx of kidney stones First stone Recurrent stone
24 Urine Collection
High/N Calcium
Blood test
Uric Acid >750mg/day (women)
>800mg/day (men) Oxalate <40mg/day
Citrate <550mg/day (women) <450mg/day (men) Calcium
>250mg/day (women) >300mg/day (men)
Urine Vol <2L High PTH
Hyperparathyroidism
Bicarbonate
RTA
Progressive calculi (increasing in size or number) Children, Non-caucasians Non calcium containing calculi Solitary kidney xt
Increase fluid intake Aim UV >2L/day Lower salt intake
Thiazide
Urine pH <6.5
Potassium Citrate Low oxalate diet ↑Calcium in diet
↓Purine diet Weight loss Allopurinol
UTI? Rx UTI
Imaging Imaging
Low/Low N
Yes
No
No
Yes Labs
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Summary • Renal stones is increasing in incidence • First timers may not need to be evaluated, however • Further evaluation is necessary in certain circumstances
o Multiple/recurrent stones o Progressive calculi (increasing in size or number) o Children, Non-caucasians o Non calcium containing calculi o Solitary kidney o Metabolic syndrome
• In the acute setting medical therapy can be attempted (if stones are <7mm) and surgical options pursued if needed
• General advice to increase fluid intake, salt/oxalate/animal protein restriction and normal calcium diet is applicable to most patients
• Further treatment options can be tailored based on biochemical findings
• Follow-up is required to avoid long term sequelae from chronic renal calculi
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Recommended reading
• Elaine M. Worcester and Fredric L. Coe.Calcium Kidney Stones.NEJM 2010;363:954-63.
• Khashayar Sakhaee, Naim M. Maalouf, and Bridget Sinnott. Kidney Stones 2012: Pathogenesis, Diagnosis, and Management. J Clin Endocrinol Metab 97: 1847–1860, 2012.